Normal cardiovascular adaptations in pregnancy include generalized vasodilatation and reduced uterine and systemic vasoconstrictor responses to infused angiotensin II (ANG II). The specific physiologic, biochemical, and molecular mechanism(s) by which pregnancy alters uterine and systemic flows remain unknown, although it clearly results from both vasodilatation as well as growth/neovascularization. Uteroplacental vasodilation and angiogenesis are associated with increased secretion of basic Fibroblast Growth Factor (bFGF), Epidermal Growth Factor (EGF), and Vascular Endothelial Growth Factor (VEGF) as well as placental derived estrogen and progesterone during the second and third trimesters of pregnancy, at a time when fetal growth and uteroplacental blood flows increase dramatically. This increase in blood flow contributes to dramatic increases in shear stress on the lumenal surface of the vasculature. The uteroplacental vasculature in pregnancy exhibits very prominent production of Nitric Oxide (NO) and Prostacyclin (PGI2) from the endothelium due to increased expression (protein and mRNA) of endothelial NO synthase (eNOS) and cyclooxygenase-1 (COX-1), respectively. The overall hypothesis of this project is that uterine artery endothelium-derived NO and PGI2 productions are increased in normal pregnancy because these vessels are exposed to angiogenic growth factors (e.g. bFGF, EGF, and VEGF), placental steroids (Estrogen and Progesterone), and shear stress. We will examine these specific aims; AIM I Determination of the physiologic factors during the second and third trimester of ovine pregnancy controlling uterine blood flow (UBF) and the in vivo expression of eNOS, COX-1 and PG12 synthase (PGIS) by evaluating the local effects of: (Exp. 1) unilateral uterine arterial infusion of the estrogen receptor antagonist ICI 182780; and (Exp. 2) unilateral reductions in shear stress by occluding UBF. AIM II Determination of the factors which modulate the cellular and molecular (protein and mRNA) expressions of eNOS, COX-1, and PGIS in an established uterine artery endothelial cell (UAEC) culture model derived from pregnant and nonpregnant sheep. We propose to evaluate the effects of the following treatments on NO2/NO3 and PGI2 production as well as the expression of eNOS, COX-1, and PGIS in pregnant and nonpregnant UAEC cultures: (Exp. 1) Angiogenic Growth Factors (bFGF, EGF, and VEGF); (Exp. 2) Estrogen q ICI 182,780 and Progesterone q ZK299 (i.e. q receptor antagonists); (Exp. 3) comparing static cultures vs laminar shear stress and; (Exp. 4) interactions of laminar shear stress and responses to growth factors, estrogen and progesterone. Completion of these studies will provide the framework for understanding the local control of and interactions between growth factors, placental steroids and shear stress on controlling vasodilatation and blood flow to the uteroplacental vasculature. These vasodilatory mechanisms may be reduced in pregnancies complicated by hypertension and/or fetal growth retardation.